ZK60 alloy is one of the most important commercial wrought magnesium alloys. However, it suffers from several deficiencies like severe hot crack tendency and relatively low mechanical properties as compared to aluminum alloys. In this discussion, the microstructures of a ZK60-(0, 0.5 Cu, wt.%) alloy at different heat treatment states were examined by various techniques including optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The corresponding room temperature tensile properties of the alloys were also tested. The results indicate that trace Cu addition could dramatically improve the casting properties and tensile performance of the ZK60 alloy. In the peak-aged condition, for example, the ultimate tensile strength and relative elongation were 261.4 MPa and 17.51% for the current ZK60-0.5Cu alloy, in contrast to 222.9 MPa and 5.97% for the ZK60 alloy, respectively. The improvements could be mainly attributed to the elevated number density and refinement of the dominant strengthening phase β1΄, together with the presence of C15 Laves phase MgZnCu formed in the ZK60-0.5Cu alloy. In addition, no appreciable change in yield strength was observed.